Sample consumable and loader

ABSTRACT

A sample consumable that carries a microvolume of sample to a sample loader. The consumable is precisely aligned utilizing a double-alignment feature to the loader. The loader is based on a crank-slider geometry and allows for simple, one-handed operation for the user. Overall, the consumable and sample loader increase reproducibility of in-line sample loading and offers ease-of-use.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. provisionalapplication No. 61/952,014, filed on Mar. 12, 2014, the entiredisclosure of which is incorporated by reference as if set forth in itsentirety herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under NationalInstitutes of Health Grant #5 R44 HL099092-03. The government hascertain rights in the invention.

FIELD

The present invention relates to sample loading for miniature fluidicsystems, and particularly to the macro-to-micro sample loading problem.

BACKGROUND

Sample loading into biological instruments and devices with fluidicsystems currently requires large sample volumes, typically greater than100 μL. In biology and science, samples are precious and often there isa desire to use as small a volume as possible. This is exemplified inthe “world-to-chip” problem, where microfluidic devices are capable ofhandling volumes <1 μL, but it is difficult to load a sample of thatsize into the device. The “world” can include biological, chemical, andclinical samples that are derived from experiments, blood, and otherbiological fluidics. The ability to fabricate increasingly smallerchannels in glass, fused silica, and other materials throughphotolithography further emphasizes the importance of solving thisproblem.

This sample loading problem is present in flow-based systems, such asflow cytometers, where a moving fluid flow carries a sample to a laserdetection region for analysis. Current methods of sample loading for aflow cytometer, or similar types of flow-based instruments, includeutilizing a sample withdrawal tube for “sipping” the sample. Thisapproach typically requires 200 μL of sample, of which only 50 μL may bewithdrawn and analyzed. While the sample injection tube is flushedbetween uses, there is still the possibility of cross-contamination.This leads to a waste of 150 μL of sample, which for fear ofcontamination cannot be returned to its original source.

Lab-on-valve devices also require sample injection. In these systems, arotating valve allows selection among the different types of samplesintroduced into the system. Sample introduction is typicallyaccomplished using syringes attached to the inlet ports. Microvolumesyringes exist but they are typically expensive for single-useapplications.

Sample injection is also important in various types of chromatography.In chromatography systems, after the sample is injected by the syringe,there is sometimes a rotary diaphragm valve that is utilized to loadprecise volumes of samples into flow based systems. A certain samplevolume is introduced by the syringe. This sample fills a section ofchannel. The diaphragm valve is rotated to bring the filled channel toconnect with a carrier fluid and the entrance to the column. Movement ofthe carrier fluid displaces the sample. This approach allows a preciseamount of volume to be delivered to the system. The diaphragm valveapproach for sample loading thus requires a syringe for sample injectionand a rotary valve for fluid metering,

The presence or absence of bubbles at either end of the sample canimpact the loading profile of the sample into the system. The desiredloading profile for a sample can take one of several configurations:bubble in front, bubble in back, bubble on both sides, and no bubbles.The bubble interface introduces plug flow on that side of the sample,whereas no bubble leads to a stretched sample as it goes through thesystem. No bubble on both sides leads to a long transit time for thesample through the system and the greatest amount of sample dilution. Along transit time may not be desirable if the sample analysis time is tobe short. Conversely, bubbles on both sides may not be desirable if somesample dilution is required. The ideal sample loading may be a bubble onone end, preferably the back end of the sample, such that the front endhas a parabolic profile and some sample dilution.

A diversity of methods can be utilized to address this problem,including inserting a capillary in-line with tubing, using U-shapedconsumables, dummy consumables, in-line loaders, and variations thereof.One can also exclude a bubble based on inserting a pin into thecapillary as well as making one end of the capillary contact first priorto the other end. These approaches are complex and further simplicity isdesirable.

SUMMARY

Embodiments of the present invention provide an improved approach tosample loading using a consumable with a sample region that can bereadily inserted in-line into a custom sample loader. Variousembodiments of the consumable include a double-alignment feature, tab,air pocket, and precise capillary volume, among other features.

The sample loader has two halves that form a fluid seal when closed.When open, there is a slot for the consumable with the sample to beloaded in-line with the system. Both the consumable and the sampleloader have specific geometries that either eliminate or introduce abubble into the loaded sample, thus permitting the creation of a desiredloading profile. Furthermore, embodiments of the sample loader featuregeometries that allow for one-handed operation, facilitating theone-handed introduction of the consumable into the system.

In one aspect, the present invention concerns a consumable for loading asample. The consumable comprises a body, an inner alignment featuredisposed within the body for aligning the consumable with a loader, andan outer alignment feature for aligning the consumable with the loader.The body may be fabricated from a transparent material.

In one embodiment, the body is cylindrical and the outer alignmentfeature is the cylindrical shape of the body. In one embodiment, theconsumable further comprises a tab that extends from the body. In oneembodiment, the consumable may comprise an air pocket connecting thecapillary and the loading region.

In one embodiment, the consumable further includes a capillary forholding a sample and a loading region connected to the capillary forloading the capillary, wherein the loading region is substantiallylarger than the capillary. The capillary may be concentric with theinner alignment feature and the outer alignment feature. The capillarymay be tapered.

In another aspect, the present invention relates to a loader forreceiving a consumable holding a sample. The loader includes a sliderplunger, a door crank, and a rod that aligns to the outside surface ofthe loaded consumable. The loader may be configured for one-handedoperation. The consumable may be cylindrical.

In one embodiment, the loader further comprises a latch and the sliderplunger is spring loaded, the actuation of the latch causing the sliderplunger to open the door crank for loading a consumable. In oneembodiment, the loader further comprises a receptacle for the consumableand a gasket disposed therein, and when the loader is closed the sliderplunger forms a seal with the back of the consumable and the front endof the consumable forms a seal with the gasket. In one embodiment, theloader further comprises a needle for penetrating a capillary in theconsumable.

In yet another aspect, the present invention relates to a method foranalyzing a sample. The method includes loading the sample into acapillary disposed within a consumable, loading the consumable into aloader, and closing the loader, thereby forming a seal between a sliderplunger and the back of the consumable and a seal between a gasket andthe front of the consumable. The loading and closing may be performedone-handed. The consumable may be cylindrical.

In one embodiment, the method further comprises actuating a latch tocause the slider plunger to open a door crank for loading theconsumable. Loading the consumable into a loader may comprise placingthe consumable in contact with at least one guide rail. The consumablemay be loaded by the handling of a tab on the consumable.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an exemplary consumable in accord with the presentinvention;

FIG. 2 shows the consumable of FIG. 1 in a three-dimensional view;

FIG. 3 shows one method for loading a sample into the consumable ofFIGS. 1 and 2;

FIG. 4 illustrates an exemplary crank-slider sample loader in accordwith the present invention;

FIG. 5 presents the sample loader of FIG. 4 in side profile, showing thethree different states of the loader: closed without consumable, closedwith the consumable, and open with the consumable; and

FIG. 6 shows a three-dimensional view of the loader of FIGS. 4 and 5 inits various states.

DETAILED DESCRIPTION

Overview

A consumable should be easily handled by all users. The user should beable to easily hold onto it and be able to load it into the system.There should a region for holding the sample in the consumable. Thefilling of this sample region should be easy and avoid unintentional airbubbles. A consumable should be readily loaded into the system and formfluid seals reproducibility.

Embodiments of the consumable in accord with the present inventionaddress these different complexities and requirements by having adouble-alignment feature, internal tapered capillary, defined samplevolume, defined air pocket, clear material, and a tab grip. Thedouble-alignment feature allows precision alignment of the consumable inthe system, allowing for failsafe sample loading. The internal taperedcapillary has a defined volume so that fluid forms a positive convexityat the front end of the capillary, allowing for a bubble-free seal atthe front end. There is a defined air pocket at the back of the samplebased on geometric features of the consumable. The consumable is madefrom a clear or translucent material, allowing for visualization of thesample. It also has a tab grip for easy handling.

The consumable addresses several major challenges of sample loading:bubble in back and no bubble in front, ergonomic design, proper samplefilling, reproducible sample loading, and ease-of-use. The particularloading profile, bubble in back and no bubble in front, is importantbecause of the dilution and transit time experienced by the analysistime.

The sample loader accepts the consumable and has an inlet and outlet forfluid. The sample loader has a minimum of two different states, one withand one without the consumable. In the absence of the consumable, thesample loader makes a seal and fluid is able to pass through the system.This is the closed state of the sample loader. When the consumable ispresent, the sample loader is able to direct fluid through theconsumable, displacing the sample, and thus moving the sample into thesystem. Other states of the loader can include the open state, which canallow the consumable to be loaded into the system.

The sample loader should have one-handed operation, i.e., that the usercan open the loader and load the consumable with one hand. This isimportant because the user may be in a non-laboratory environment thatprevents use of their other hand. This means that the sample loadershould remain open by itself during loading so that the consumable canbe loaded into the system. Once the consumable is loaded, the loadershould be able to be closed with one hand.

The loader also needs to have precision alignment features to accept theconsumable. These alignment features should be robust and lead toreproducible sample loading. The alignment should have a place forlocating the consumable as well as alignment to the inlets and outletsof the sample loader.

Another aspect of the sample loader in accord with the present inventionis based on a crank-slider mechanism. A crank-slider is a mechanicalmeans of translating rotational motion into linear motion. Embodimentsof the invention utilize this mechanism coupled with a spring-basedmechanism that seals around the consumable.

There is a latch on the crank-slider loader that allows it to be closed.When the latch is pressed, the system is spring-loaded and the dooropens automatically. The open door allows the user to insert theconsumable in a one-handed method. The crank-slider utilizes metalshafts for precision alignment of the consumable with the consumablereceptable. An o-ring mates to the back of the consumable and theconsumable is sealed to a flat gasket at the front.

One aspect of the invention concerns a method for loading a smallmicrovolume of sample in-line with tubing and a fluidic system. Theconsumable holds the sample and the mechanical loader receives theconsumable. The consumable transfers the sample to the loader. Theloader forms fluid seals on both sides of the sample and allows pressuredriven flow to move the sample into the system. Depending on thegeometry of both the consumable and the loader, bubbles can beeliminated or added to have the desired loading profile.

Embodiments of the present invention can introduce a sample in-line witha flow path in a way that is low-cost and easy-to-use. The consumableand loader are manufacturable using existing production methods, such asinjection molding, extrusion, stamping, or other commercially-availablemethods.

Consumable

One embodiment of the consumable is shown in FIGS. 1-3. With referenceto FIG. 1, the consumable has a tab for holding, a capillary for holdingthe sample, an area for a back air pocket, and a double-alignmentfeature. The main body is cylindrical with a tab for easy handling andergonomics. The material is transparent to allow visualization of thesample. The container allows for fluid sealing on both ends to preventleaks during operation.

The consumable's double-alignment feature guides its loading directlyin-line with the sample loader. Precision alignment with the loader isimportant since the tolerance to alignment ranges from ±0.005″ to±0.010″. Inability to precisely align the consumable with the loader canlead to leaks and loss of sample. These tolerances can be difficult toattain, especially when each loader and consumable is mass manufactured.

The double-alignment feature is implemented in two parts. The outerbarrel of the consumable is cylindrical. This feature allows it to siton guide rails on the loader. A cylindrical shape allows the user toinsert it from a variety of positions and, regardless, it willself-align with the loader's cylindrical receptacle. The inner barrel ofthe consumable is also cylindrical and may have a taper to allow for aprecise fit. The inner barrel of the consumable mates with the loader'scylindrical receptacle.

As shown in FIG. 1, the inner capillary channel is concentric with thedouble-alignment feature. This allows the capillary to be directly linedup with the gasket and the exit needle of the sample loader. It isimportant that the exit barrel of the capillary form a seal around theexit needle, otherwise leaks will occur. The reproducibility ofalignment needs to be very high, and the exit needle size is typically28 gauge (0.01425″). The size of this needle dictates the precision ofthe alignment.

The consumable may have a tab for easy handling. The tab feature isergonomic and allows the user to hold onto the consumable readily. Byholding onto the tab feature, the user can easily pipette the sampleinto the inner capillary barrel of the consumable. This allows for readyvisualization of the filling capillary. The tab is molded from theplastic housing. Its size should accommodate the diversity of fingersizes, from extra small to extra large.

A preferred loading profile of the sample in flow cytometry applicationsis no bubble in front and a bubble in the back. This allows for ananalysis time of approximately 1-2 minutes for a 10 μL sample. Nobubbles on both ends would lead to a much longer analysis time andtherefore is not desired. Bubbles on both sides would lead to not enoughsample dilution and too fast a transit time. In order to attain thisloading profile, the consumable needs to have appropriate features. Thefirst is an area for an air pocket on the consumable. This isaccomplished by having a larger recessed area on the back pocket of theconsumable. The capillary fill area is separate from this. When theloader's o-ring seal forms on the back of the capillary, it forms aroundthe larger recessed area. Thus, when fluid is passed through theconsumable to drive the sample into the system, the air pocket resideson the back of the sample. Therefore, a consumable with a recess forforming an air pocket helps ensure that a bubble forms on the back ofthe sample.

Forming a bubble-free interface can be accomplished in a variety ofways. A first method is to design the capillary volume to be less thanthe actual fill volume so that fluid forms a positive convexity at thefront end of the capillary. For instance, if the pipetted sample is 10μL, then the capillary volume can be 9.5 μL, or 0.5 μL less than thepipetted volume. The excess volume forms a positive convexity at thefront end of the capillary. When this consumable and sample is loadedinto the loader that has been primed, it will form a bubble-free seal atthe front end of the consumable.

An alternate method of forming a bubble-free seal at either end of thecapillary is to have a short section of a blunt needle protrude into thecapillary. The insertion of the needle into the capillary displaces anypotential air at the ends of the capillary, allowing for a robust,bubble-free seal. The length of the needle protrusion and its gaugedetermines how much air can be displaced. This volume can be adjusted bychanging the needle gauge and its protrusion length. The blunt needleswill need to be primed prior to being inserted to ensure that there isno air in the needles. In all cases, failure to attain the desired typeof seal will compromise the integrity of the diagnostic test.

The consumable has two ends where it can form fluid tight seals. Thefront end of the consumable presses against a gasket. The spring-basedloader presses and seals against the back of the consumable. Overall,the spring-based force along the axis of the consumable allows seals tobe formed at both ends. It is important that the seal is on-axis so thatfluid passes through the seals and the capillary without blockage. Thismeans that the alignment mechanism must be precise for the consumableand the loader.

The consumable's capillary volume is preferably defined to range from5-100 μL. Volumes outside this range can also be accommodated. Thevolume is based on the capillary fill volume within the capillary.Capillary diameters in the range from 0.020″ to 0.060″ are typical butit can be larger or smaller to fully accommodate the desired volume. Thecapillary can be tapered or flared to accommodate a certain desiredvolume. If tapered or flared, the capillary walls can be smooth so thatno bubbles are formed. The taper can be consistent with the filldirection, i.e. the larger end should be the entrance of the fluid.

The material for the consumable can be a clear or translucent materialto allow visualization of the sample. This could include polycarbonate,polymethylmethacrylate, PETG, or other similar material. The surfaceproperties of the plastic can allow the sample to appropriately wet thewalls of the capillary. This is based on a desirable contact angle withthe desired fluid to be analyzed. The surface finish of the material canbe smooth, particularly on the inside of the capillary to allow smoothfilling. Manufacture of the consumable should be free of particles,oils, or residues.

Sample Loader

The embodiment of the mechanical sample loader illustrated in FIGS. 4-6is based on a crank-slider mechanism with a latch. As shown in FIG. 5,the sample loader has three different states. The first state is closedwithout consumable. In this state, the plunger forms a seal with thegasket in the receptacle. The second state is closed with theconsumable. In this state, the plunger forms a seal to the back of theconsumable and the front end of the consumable forms a seal with thegasket in the receptacle. The third state is open with the consumable.In this state, the door is open and allows for the insertion and removalof the capillary

To operate the loader, the user presses the latch, which isspring-loaded, and the door opens. While the door is opening, theplunger translates along the rails, creating an opening for theconsumable to be loaded or removed. When the door is closed, themechanism is protected. When the door is open, the consumable andconsumable receptacle can be accessed. When the latch is pressed in thesystem, the spring force in the system opens the door. This allows forone-handed operation. The door remains open when the user inserts orremoves the consumable. This is favorable since this allows the user tohave one free hand, other than the one loading the consumable. Closingthe door moves the plunger towards the front of the crank-slider, thuscreating a seal on the back of the consumable or the front gasket.

The loader is based on a mechanical crank-slider. Opening of the door, arotational movement, directly translates the plunger that makes the sealwith the consumable or opposing gasket. The plunger is translated alongtwo rails that guide the motion of the plunger. One advantage of thisapproach is that the door closes over the mechanical hardware, allowingit to be hidden and thus enhancing user appeal. The travel of theplunger is directly related to the linkages. This is geometricallycalculated. Overall, the use of a crank-slider enables the one-handedloading method and increases the user appeal of the instrument.

The plunger is the slide on the loader. It translates along two ⅛″diameter metal rods that serve as alignment rails. The plunger has inlettubing and an o-ring for sealing to the consumable or opposing gasket.Furthermore, there is a spring platform that pushes on two compressionsprings. The purpose of the spring platform and springs is to compensatefor the presence and absence of the consumable. Essentially, thiscreates a variable length plunger that can form a seal with or withoutthe consumable. The extended and compressed spring length needs toaccommodate for the length of the consumable.

The crank-slider loader needs to form fluid tight seals in the presenceand absence of the consumable. The spring-loaded plunger allows this tohappen. The plunger has an o-ring or an equivalent means of sealing.This o-ring, with the assistance of the spring force, either pressesagainst the consumable or the gasket in the receptacle on the loader.The receptacle on the front part of the loader has a gasket with a 27gauge blunt needle passing through its center. The o-ring on the plungerhas a larger inner diameter than the gauge of the needle such that itforms a fluid seal around the entrance to the needle when the loader isin its closed position without the consumable. In the presence of theconsumable, the plunger's o-ring mates to the back of the consumable.The consumable tip forms a seal against the gasket. The inner diameterof the consumable tip seals around the entrance to the blunt tip needle.In this manner, the double-alignment feature of the consumable is veryimportant.

Elimination of bubbles at the front end of the consumable is important.In order to do this, the loader needs to be primed with fluid in theabsence of a consumable. This purges any bubbles from the system andalso wets the gasket in the receptacle on the loader. After theflushing, it is important to clamp the entrance and exit tubing toprevent reformation of any bubbles at the interfaces. With thisapproach, a drop of fluid remains on the gasket after priming andopening. This small drop of fluid then mates with the fluid convexity onthe consumable, ensuring a fluid-to-fluid contact. In this scenario, theblunt needle tip is flush with the gasket and there is no requirement ofprotrusion of the blunt needle tip into the lumen of the capillary. Inan alternate scenario, the blunt needle tip can protrude beyond theplane of the gasket and protrude into the lumen of the capillary. Inthis manner, the volume of the needle displaces any air at the tip ofthe capillary. This approach is suitable if there is a small amount ofair at the tip of the consumable. The presence of the blunt needle tipin the lumen, however, creates a small dead volume that may not bedesirable.

A latch is utilized to lock the door in place. The latch preventsinadvertent opening of the door. The latch needs to be pressed in orderfor the door to open. The latch is displaced when the door is presseddown. The latch meets the requirement of using a single hand opening andclosing the device. Two torsion springs control the movement of thelatch. They return the latch to its original position after the latch ispressed. The latch should be in its neutral position when the door isclosed. This means that the latch can be able to withstand the naturalopening force of the door due to the springs in the plunger.

EQUIVALENTS

Those skilled in the art will recognize, or be able to ascertain usingno more than routine experimentation and/or engineering, manyequivalents to the specific embodiments of the invention describedherein. The scope of the present invention is not intended to be limitedto the above Description, but rather is as set forth in the claims thatfollow.

The invention claimed is:
 1. A consumable for loading a sample, theconsumable comprising: a body having a sample loading end and adifferent exit end; a capillary for holding a sample, the capillary openat both the sample loading end and the exit end and providing a fluidpathway through the body from the sample loading end to the exit end; aninner alignment feature disposed within the body for aligning theconsumable with a loader, the inner alignment feature having an outersurface not in contact with the capillary; and an outer alignmentfeature for aligning the consumable with the loader, the outer alignmentfeature having an inner surface facing the outer surface of the inneralignment feature, wherein the outer surface of the inner alignmentfeature is concentrically encompassed by the inner surface of the outeralignment feature.
 2. The consumable of claim 1, wherein the body iscylindrical and the outer alignment feature is the cylindrical shape ofthe body.
 3. The consumable of claim 1 further comprising a tab thatextends from the body.
 4. The consumable of claim 1 further comprising aloading region connected to the capillary for loading the capillary,wherein the loading region is larger than the capillary.
 5. Theconsumable of claim 4 wherein the capillary is concentric with the inneralignment feature and the outer alignment feature.
 6. The consumable ofclaim 4 further comprising an air pocket connecting the capillary andthe loading region.
 7. The consumable of claim 4 wherein the capillaryis tapered.
 8. The consumable of claim 1 wherein the body is fabricatedfrom a transparent material.
 9. The consumable of claim 1 wherein theinner alignment feature concentrically encompasses the capillary. 10.The consumable of claim 1, wherein the sample loading end has a firstdiameter and the sample exit end has a second diameter, and whereinratio of the size of the first diameter to the size of the seconddiameter is no larger than 3:1.
 11. The consumable of claim 1, whereinthe diameter of the capillary is no larger than 0.060″.
 12. Theconsumable of claim 11, wherein the diameter of the capillary is between0.020″ and 0.060″.
 13. The consumable of claim 1, wherein the consumableis configured to form a fluid seal at the sample loading end and thedifferent exit end during operation.